Generally, each roll of a winding equipment in a rolling factory suffers abrasion due to: corrosive environment caused by contact with cooling water and high temperature passing plate material (900.degree. C. or less); sliding on the passing plate material; and impact at the time of inrushing of the passing plate material.
Performance required for, each roll includes, mainly, gripping force on passing plate material (a friction coefficient), plate flaw (slip flaw and flaw by seizure) resistance, and the like.
As for an arrangement of rolls, as shown in FIG. 2, an equipment for winding and coiling high temperature plate material 10 of 400-900.degree. C., which has been rolled to standard size, comprises, for each coiler, upper and lower pinch rolls 11, 1, and wrapper rolls (unit rolls) 6-9 located around each coiler mandrel, and sometimes, comprises pinch rolls 11, 1 located independently in front of a group of coilers. The pinch rolls and wrapper rolls perform tension adjustment, conveyance, and a change of direction, between apparatuses after and before them, i.e., between a finishing mill and a coiler, contributing to smooth winding in the coiler and to putting a winding shape in good order.
Surfaces of the pinch rolls 1 shown in FIG. 2 suffer abrasion due to contact with and slide on the high temperature passing plate material 10 accompanying pressing force of the upper pinch rolls 11, and due to corrosion by cooling water. Further, the wrapper rolls (unit rolls) are used in the similar severe conditions.
If a shape of a roll body is changed by the above-described abrasion, it accompanies changes in the pinch force and pressing force on the passing plate material, and becomes cause of deformation of the winding shape and generation of plate flaws. Therefore, usually, each roll is exchanged in a short life period of about one month, producing a great loss respecting an operating ratio of the equipment and repair cost.
For pinching and conveying the passing plate material, it is necessary to ensure a suitable friction coefficient of the roll surface. When the value of the friction coefficient is small, there arises severe slips or seizure, inviting a loss such as flaws in the passing plate material, exchange of rolls, or the like.
As a roll in the winding equipment, one of the steel group such as a hardened buildup product, a tinned product, or a forged steel product is mainly used. Those products, however, have reached their limit of performance for attaining both the abrasion resistance and plate flaw resistance, and attaining stable operation and stable operational cost property. These products do not have sufficient abrasion resistance, conveyance resistance, and plate flaw resistance at the same time.
Japanese Laid-Open Unexamined Patent Publication No. 55-149710 suggests a roll having spalling resistance and abrasion resistance, which is obtained by hardened buildup welding with given conditions, on a surface of a roll body of the iron group, and further building up an autogenous-alloy-sprayed layer on the welded surface. The object of that invention, however, is very wide one, "rolls relating to iron manufacturing".
As for the lower pinch roll, importance lies in its performance in applying a pinch force on the passing plate material and maintaining suitable conveyance property, so as to prevent plate flaws and to put a winding shape in good order.
According to the specifications of the surface film of the roll according to Japanese Laid-Open Unexamined Patent Publication No. 55-149710, the friction coefficient is in an extremely low level, which becomes cause of plate flaws and unstableness of the winding shape due to deficiency of a gripping force on a plate material and generation of slips.
One of the present applicants previously proposed a roll for a winder in a rolling factory, which has high durability (Japanese Patent Application No. 6-282490 filed on Oct. 24, 1994, i.e. Japanese Patent Publication (Kokai) No. 5-121464).
This earlier invention, however, limits the roll proposed in Japanese Laid-Open Unexamined Patent Publication No. 55-149710 into the scope of the "roll for a winder in a rolling factory", and the material for the autogenous alloy spraying also remains to be one of the wide range of component types generally used, i.e., Ni-base material, Co-base material, and Fe-base material. From the viewpoint of roll performance, the roll applied with said material for spraying is limited in improvement in the abrasion resistance, and the value of its friction coefficient which has close relationship to the conveyance property for passing plate material is small, having weakness for smooth passing of the plate material.
An object of the present invention is to provide a roll of a winding equipment, which has been improved in the abrasion resistance, passing plate resistance, and plate flaw resistance, for solving the problems relating to the operating ratio of the equipment, repair cost, and quality assurance for the passing plate product.